The invention relates to an impulse discharge lamp having a hollow gas-filled cylindrical discharge receptacle, preferably filled with an inert gas, which receptacle is provided at each of its respective ends with an electrode which is secured in vacuum-tight relation thereto.
Rod-shaped impulse discharge lamps of conventional construction comprise a glass or quartz tube having a respective rod-shaped electrode at each end of the structure with the electrodes extending into the discharge chamber with the latter being suitably melted to effect an axial fusing of the associated rod therewith. Both electrodes extend into the discharge chamber with the internal end portion of the electrode, not coated with glass, operative to feed the plasma with the energy needed for the generation of the light flash. For technical reasons involved in the production, the glass beading or bulge of the securement has a length of several millimeters at the sealing. In addition, the internal electrode ends, which are not coated with glass, also must extend several millimeters into the internal chamber of the impulse discharge lamp, so that the inner electrode end can effectively carry a central body containing suitable activation material, and at the same time the electrode end will not be locally overheated by excessively high current densities, and be brought to vaporization.
In a newer construction of impulse discharge lamps, two metal discs, produced from a material which is suitable for fusing, are fused onto the respective end faces of a glass tube, with the diameter of such discs being larger than the internal diameter of the tube at the point of fusing. In this construction the electrical energy is fed to the plasma across the internal surface areas of the discs. Likewise, the external length of an impulse discharge lamp constructed in this manner is greater than the effective internal length, i.e. the distance between the two active inner surfaces of the electrodes, by merely twice the thickness of the metal discs. In the production of impulse discharge lamps of this later construction, the glass tube is cut size, and it, with the two electrodes, are disposed in predetermined positions relative to one another within a suitable receptacle. Following evacuation, the receptacle is filled with inert gas, preferably Xenon. The respective electrodes are then heated inductively and pressed against the glass ends of the tube to thereby fuse the electrodes thereto in vacuum-tight relation. The inert gas subsequently is pumped out of the receptacle and the assembled impulse discharge lamp removed therefrom.
In the production of the initially mentioned impulse discharge lamps, of conventional construction, the glass-tube itself may be considered to function as its own receptacle, and is initially sealed at one end in vacuum-tight relation, following which the electrodes are disposed loosely into the rough glass tube and the open end thereof connected to a pump to evacuate the tube, which is thereafter filled with inert gas. The free end of the tube may then be sealed by a temporary closure thereof to permit separation from the pump, following which the movable electrodes are brought into the desired positions within the tube and the latter melted at the desired points to effect a fusing thereof while the tube is in a vacuum-tight condition. The excessive protruding glass portions at each end are subsequently cut off.
It will be appreciated that this type of production procedure has substantial advantages in connection with the production of the first described type of impulse discharge lamp. First, the mechanical expense for the same production quantity can be kept substantially lower. Further, the gas with which the tube is to be filled is not contaminated by foreign gases absorbed during each pumping operation, resulting from the desorption on the inner walls of the receptacle, the mounting structure or jig for the tube and electrodes, on high frequency coils, and/or other parts. In addition, the conventional type of procedure produces impulse discharge lamps in which the fused metal-glass joint between tube and electrode is not stressed for tension forces but rather for shear forces resulting from the high internal pressures which occur during discharge. As a result, the operating safety of impulse discharge lamps produced in this manner is increased, as glass-metal unions have only a relatively low strength with respect to tension stresses.